Spark plug



1 JWMLABLE WP" Aug. 17,1926. 1,596,685

w. L. REARDON SPARK PLUG ginal Filed July 3 192 t a, E

\z mm? 11 IN VEN TOR.

il ilfiaariazi ATTORNEY,

Patented Aug. 17, 1926.

' UNITED STATES BEST AVAlLA BtE COPE 1,595,685 P m ered.::

WILLIAM L. REARDON, on Home, rrimnoisu SPARK PLUG.

Application filed July 3, 1922, Serial No. 572,480. Renewed April 30, 1926.

This invention relates to improvements in spark plugs.

Said invention pertains more particularly to a spark plug of the double end variety or that having terminals at each of its ends whereby said plug may be reversed in position in the cylinder head.

The objects of the invention are to provide a spark plug of the doublcend type that, by reason of the peculiar manner in which it is constructed and assembled, will be free of compression leaks around the parts or between them; there will be no danger of internal short circuits; that an intensifying of the spark at the terminals within the combustion chamber will result from the employment of an external spark gap; that the: condition of the plug at the inner firing; terminals may be determined by observing the form andcondition of the spark atthe-outer terminals; and that when the said inner terminals become fouled as indicated by the appearance of thespark at said outer terminals, the plug may be reversed in position thus presenting clean terminals to the firing charge.

To the end that the invention may be thoroughly. understood I have provided the accompanying drawing forming part hereof wherein Figure 1 is a side elevation of the plug of my invention. p -Figure 2 is a similar view showing one half of the plug in longitudinal section- Y Figure2 3 is a plan of the plug. as viewed at one of its. ends, andv v 1 v' Figure 4 is a detail, in section, ofpart of one of the shell portions of the plug.

The plug includes two metal shell-portions 1, 2 each having a base 3, one of which is shown at the left of Figure 2, each said portion being externally threaded, as in common practice,,to engage the. threads of the cylinder head, not shown, and the inner end of each ofthe shell-portions is reduced to a comparatively thin edge as shown at 4 in Figure 4, the purpose of which will now appear. H

E The said bore 3 is enlarged asshown at 5 and receives into it aporcelai n insulator 6 ofa form that will fit into the said enlarged bore 5 in a fairly snug manner and rest upon a shoulder 7 of the shell, there being a gasket 8 between said shoulder and the insulator forming a tight closure" .The said insulator is reduced in diameter at its inner end leaving a shoulder 9 to receive a gasket 10, the edge at of the shell being swedged inwardly upon it making an absolutely leak tight joint, :1 filling of cement being interposed between the insulator (5 and the shell, if desired, before resorting to the swedging process.

The complete plug is made up of two companion portions of the construction just described, it being observed in Figure 2 that the insulators 6 of each abut one against the other spacing the shells apart the distance required to prevent a spark jumping from one'to the other.

Preferably, as in common practice, the outer ends of the insulators are reduced considerably in diameter ,and extend toward the outer ends of .the'shells.,Furthermore, the

insulators are 'providedwith bores 63 centrally and longitudinally to receive a doubleend terminalrod, or. electrode, whose exremities are designated at 11. Said rod midway its length has an enlargement 12 and is roughed preferably by providing screw threads 13, while midway of the enlargement is a flange 14-. i

Thebores 6. vof the insulators receive the enlargements l2 and are preferably threaded, andthe abutting ends are recessed at 15 to ;receive.into'them the said flange leflof the said elect'rode '111. z I In assembling the plugthe shell portions 1, 2. arecompletedas described whereupon cement of a kind that will become vitrified under a baking-heat is placed in the enla'rged bores of theinsulators,.the terminal rod or elect-rodev being ,then inserted and screwed intqthe plasticcement, such cement the, entranceof the rod,'fbeing also carried down into the smaller bore that re ceives the outer end of the electrode. Having thus completed onehalf. of the plug, an insulatingsleeve 16 is placed over the insulator 6 of that half, the other half having been treated to the cement is screwed upon the enlargement l2 and finally forced against th'esaid sleeve 16, the cement filling any and .all.,spaces around the flange let. When complete, the plug is placed in an oven. to xgit rify thecement filling, after which the;plug is ready for use.

The, sleeve 16.serves two purposes. It aids in preventing the high tension currentv jumping between the shells 2, and it also braces the; structure, being clamped be tween the said shellssothat lateral blows will not be likely to snap the poreclain in sulators 6, disrupting the plum As a convenient contact portiorr for-thecablc leading to the ignition I provide a spring clip 17 to snap around the threaded portion of the plug as a very effective and convenient connection easily attached and detached.

The threads 13 upon the enlargement 12 and the threads in thebore 6 'of'the insulators 6- provide roughened surfaces to bet tcr retain the. parts in intimate and permanent engagement. and while other roughing methods may be employed the described threads are easily formed and they assist in a mhling the parts on which they are formed.

In the strnc .uref as I provide it, the-electrodc 11, 12 is wholly insulated and widely spaced from theshell portions 1, 2 sothat sliortingi cannot occur, and sinjcethe said shell-portions are snugly closed upon the insulators there can be no-gasleaks' Fur thermore, the wide-spacing of the shell portions through the sleeve 16 and" the extended "insulator" portion abutting Within saidsleeve, the high tension current"cannot jump "from one sh'ell to the other, this being er the utmostimportance] i i Should the plu'g'bec'omefouledit may lie reversed in position and --'the -fouled end will automaticallyclean itself of accumulated oil since-the outer-endpor that outside the combustion chamber, is always aspark ga in the open air. Furthermore, the' chndi tion of the plug at its inner or firingend is reflected in the outer terminalsin that when saidihnchendbecomes'fouled a ye'l, low sparltwill appear at .tliefouter fendjh clean plug showing at -the""said"oute'r terminal' the usual; blue' Again-, the con; ditionof the ignition systein'is aliva'ysreadily determined since :iiail'uierof a' spar'k' to appear is easily noted and "the trouble can be directly traced to its source. "1 As constructed, my madeiii separate portions, as explained, so that these'al ing' of the passages by means" of the gaskets 8 and 10 by swedging of the portion 4 can be 'properly done 'without crackirilg or break; ingthe' porcelain a'swould occur Wherea one piece porcelain is employed: angli'tliereforj a thoroughly reliable article the result I Agaiinin practice porcelain or cl'a'y p'roflf not insulators niust'be baked. intense heat for severaldays, the intensity of the heatbei'ng such that metals'fivotild'become fused. It is therefore necessary "to bake such porcelains separately and then insert in the bore provided for ittheelect'rodell as the/only method that can. be used asnow known; I a v 1n othei'fwords, in order thatthe plug can be made commercially or at all, in fact, the porcelain "must be constructed and baked separately; then assembly of the separate parts is wholly practicable and a plug of commercial value is assured.

1. A spark plug of the double ignition typeincluding in its construction a pair of separate insulating cores each having in one end are'cess-for receiving' p'art of an electrode and having in its other end a bore commnnicatingwith its said recess, the bore and recess creating an opening entirely through said core, the recessed ends of said cores abnttin'g'with the'axes ol the recesses and bores in alignment. :1 single electrode lying within-the cores and e :tending through the bores and beyond the outer ends of the as embled cores, said'electrod'e having an enlargement of a considerable length at the .dleof its length to occupy the recessin each of the "coresf, a'cenient filling introduced bet-Ween the electrode enlargement and the Walls of the recesses ser ving 'with the said electrode to secure it and-the cores in connected relation, a 'sep'arate shell electrode eiiclosing cicb core andspacedfrom one another, and a sleeve of noii'conducting materialiiiterpdsed between, abutting upon, and spaci'i'i'g the last named electrodes and serv are; to brace "and p'10te'ct"==the- 1 assembled frd inlaterallireaking'strains. -f

, "s arle' phig of thedouble ignition type including i'n its construction apair of separate insulating =cores each having in a portion tlier'eof 'recfess for receiving part of an elcctrode,-andhai ing in the remaining portiona" bore communicating with its sai'cl='itece's ,"tli'e bore and recess creating an opeiiing "eiitirely tlirouglfthe core, there being a second larger, recess in the end-surface of each 'c orembmmunicating with the first recess-therein, said coresf'abutting at thei ecesse 'djn'ds 'ivith' the axes of the recesse's' 'in' aligni'nen a single electrode lying 'within the: coresextending "through the bores and beyond thefouter'nd's' of the'as semhl'ed cores and ha ving" an {enlargement of considerable length" aft-he 'rnidd-l'e -'ofj-its length lying within both-"the first named re- 'csses, said electiioide' having a further enlargement at its iiiiddlegreater in diameter than tl ie'Wirstf and lying ivithin the second named rece s and between F theassembled cores, a cement fillingintroduced between theelectro'de j'enliirgenrent'and the walls or" the rec'sses'serying with the said electrodelto se'ciiretlie latter and'tliocores in connected relation, a separate, shell electrode enclosing each'eor spaeea from onefinother, and a sleeve {of jn' oncoiidiicting" material interposed between, abutting upon, 'and spacing the last n'an'i ed' electrodes and-serving to brace and rotect tlie .assembledflcores from lateral b'i'a aiagstrziiasr. In testimony whereof I ems my signature.

1' '1 WVILLIA'M"L."REARD'ONZ 

